Regarding an indexable cutting toot in which a positive round insert and a tool body are combined, various structures for mounting the round insert to a support seat of the tool body are proposed.
A method that is disclosed in, for example, PTL 1 below is often used to mount a round insert to a tool body. In this method, the insert is positioned by contacting contact surfaces (restraining surfaces) with seat side surfaces provided in correspondence with a support seat of the tool body. The contact surfaces are formed at a constant pitch in a peripheral direction at a portion of the round insert towards a bottom surface at a periphery of the round insert by cutting portions of side surfaces of the round insert. Each contact surface is a flat surface having a tilt angle that is greater than that of the side surfaces.
In the cutting tool in PTL 1, nicks are also provided, along with the contact surfaces, at the periphery of the insert, and protrusions formed on the tool body enter the nicks. This structure is for preventing erroneous mounting of the insert. The positioning of the insert is performed by simultaneously pushing, among the plurality of restraining surfaces, two surfaces that are set at an angle of 90 degrees from each other against two seat side surfaces of the support seat.